Gonimoblast Filaments Research Articles

Morphological and Molecular Phylogenetic Analysis of a Lemanea Specimen (Batrachospermales, Rhodophyta) from China

The genus Lemanea is an evolutionally derived lineage of freshwater Rhodophyta which has a rare distribution. Morphological characterization and molecular phylogenetic analyses were conducted for a Lemanea specimen collected from Guilin, China, in this study. The results based on morphological observation and molecular evidence, including rbcL and SSU sequences, showed it was a new record of L. manipurensis Ganesan, West, Zuccarello et Rout in China. The specimen in this study was morphologically characterized by branches that were positioned in the lower part of the thallus, hair cells absent around the outer cortex, ellipsoidal and single carpospores at the top of the gonimoblast filaments and spermatangia formed in continuous wide rings on the thallus nodes. By comparing the morphology of specimens collected from Guilin, China, and the holotype specimen in India, it was found that the spermatangial shapes were variable among different populations. It was found that the presence or absence of hair cells around the outer cortex was not a reliable characteristic for the identification of the genus Lemanea based on a comparison between L. manipurensis collected in Guangxi and in India and another four Lemanea species previously recorded in China. The results of this study provided molecular evidence and a theoretical basis for molecular phylogenetic research on the genus Lemanea and enriched the species diversity and geographical distribution of Lemanea in China.

Phymatolithopsis gen. nov. (Hapalidiales, Corallinophycidae, Rhodophyta) based on molecular and morpho-anatomical evidence.

A multigene (psbA, rbcL, 18S rDNA) molecular phylogeny of the genus Phymatolithon showed a polyphyletic grouping of two monophyletic clades within the Hapalidiales. DNA sequence data integrated with morpho-anatomical comparisons of type material and of recently collected specimens were used to establish Phymatolithopsis gen. nov. with three species, P. prolixa comb. nov., the generitype, P. repanda comb. nov. and P. donghaensis sp. nov. Phymatolithopsis is sister to Mesophyllum and occurs in a clade distinct from Phymatolithon and boreal species currently assigned to Lithothamnion. Morpho-anatomically, Phymatolithopsis is comprised of species that are non-geniculate and encrusting, bear epithallial cells with rounded walls (not flared), subepithallial initials that are usually as short as or shorter than their immediate inward derivatives, conceptacle primordia from all stages forming superficially directly from subepithallial initials, mature carposporangial conceptacles with a discontinuous fusion cell, gonimoblast filaments that develop at the margins of the fusion cell around the periphery of the carposporangial conceptacle chambers, and multiporate tetra/bisporangial conceptacles. Phymatolithopsis can be distinguished from Phymatolithon by the origin of its conceptacle primordia, which are initiated superficially, directly from the layer of subepithallial initials below the epithallial cells and the distribution of gonimoblast filaments in carposporangial conceptacles, that are at the margins of the fusion cells.

<p><strong><em>S</em></strong><strong><em>arcopeltis gen. nov. </em></strong><strong>(Gigartinaceae, Rhodophyta), with <em>S</em>. <em>skottsbergii comb. nov. </em>from southern South America and<em> S. antarctica</em> <em>sp. nov.</em> from the Antarctic Peninsula</strong></p>

Gigartina skottsbergii is the currently accepted name for the large, peltate species of Gigartinaceae distributed in Argentina, Chile, and along the Antarctic Peninsula. However, phylogenetic analyses of DNA sequences for more than twenty years indicate that two species are passing under the name G. skottsbergii, and both DNA sequences and morpho-anatomy indicate that the species are assignable to an undescribed genus. To formally validate the new genus and species, we performed next generation sequencing (NGS) on the lectotype material of G. skottsbergii to document its genetic identity and obtained its complete mitogenome and partial plastid genome. Phylogenetic analysis of rbcL and cox1 sequences of the lectotype along with recent collections of G. skottsbergii from southern South America and Antarctica, confirmed the generic distinction and the presence of two morphologically similar taxa. We propose Sarcopeltis gen. nov., containing the generitype S. skottsbergii comb. nov. from southern South America, and S. antarctica sp. nov. from the Antarctic Peninsula. Sarcopeltis is characterized by the following suite of features: 1) peg-like secondary haptera that adhere to the substratum, 2) absence of an envelope surrounding each cystocarp, 3) presence of extensive, terminal, tubular gonimoblast filaments that fuse with surrounding vegetative cells, and 4) tetrasporangia formed from secondary filaments entirely in the medulla. This study demonstrates that genetic analysis of type material, together with recently obtained DNA sequences from field collected specimens, can provide clear and objective taxonomic conclusions.

Amphithallia, a genus with four-celled carpogonial branches and connecting filaments in the Corallinales (Rhodophyta)

ABSTRACTThe South African marine alga Amphithallia crassiuscula, previously subsumed in the widely reported Synarthrophyton patena, is here re-described as a distinct species and genus. Thalli grow as obligate epiphytes on Gelidium capense in the upper sublittoral zone (while S. patena grows on Ballia callitricha). Gametophytes are monoecious with four-celled carpogonial branches and sterile cells are borne on supporting cells (dioecious or hermaphroditic with two or three-celled carpogonial branches and sterile cells borne on hypogynous cells in Synarthrophyton). Postfertilization stages involve a connecting filament linking the carpogonium to several putative auxiliary cells, demonstrating a non-procarpic condition with apparent absence of a fusion cell. Gonimoblast filaments develop at the level of basal cells of carpogonial branches. Spermatangial mother cells remain either unbranched (cutting off spermatangia only) or develop dendroid (branched) filaments with terminal spermatangia (as in Synarthrophyton). Multiporate conceptacles develop straight pore canals lined by non-differentiated cells (conical canals with differentiated pore cells along the base in Synarthrophyton). The here described pre- and post-fertilization characters are new for the order Corallinales motivating the establishment of the new genus Amphithallia.

Revision ofBatrachospermumSectionVirescentia(Batrachospermales, Rhodophyta) with the Establishment of the New Genus,VirescentiaStat. nov.

In recent years, sections of the paraphyletic genus Batrachospermum have been investigated using DNA sequence data, as well as morphology and some have been raised to genera in order to resolve this paraphylly. The species of Batrachospermum section Virescentia form a well-supported clade and we propose the raising of this section to the genus Virescentia stat. nov. In addition, we re-evaluated the characters used to circumscribe species by reexamination of type specimens and new collections in historically important areas. Of the eleven previously accepted species, we recognize five species and a new species is proposed as follows: V. crispata, V. gulbenkiana (synomyms V. azeredoi and V. ferreri), V. helminthosa (type species), V. viride-americana sp. nov., V. viride-brasiliensis and V. vogesiaca. The species are circumscribed on the basis of morphological characteristics (shape of fascicles, occurrence of secondary fascicles, disposition of carpogonial branches and size of carpogonia), geographic distribution, and DNA sequence data (rbcL and COI-5P). Descriptions, identification key and photomicrographs are presented for each recognized species. Two potential species from Japan based on DNA sequence data remained undescribed due to lack of voucher specimens for morphological observation. Other species previously assigned to the section Virescentia are referred to other genera of Batrachospermales based on morphology (disposition of carpogonial branches, shape of trichogynes, types of gonimoblast filaments and arrangement of carposporophytes).

The Phyllophoraceae (Gigartinales, Rhodophyta) from Peru with descriptions of Acletoa tarazonae gen. & sp. nov. and Gymnogongrus caespitosus sp. nov.

:We investigated species in the family Phyllophoraceae from Peru using sequences of the plastid rbcL sequences and morphological examination. Here we describe Acletoa tarazonae gen. & sp. nov., characterized by the presence of secondary medullary cells around cystocarps, gonimoblast initials that are downwardly and upwardly directed, and a linear arrangement of gonimoblast filaments on medullary cells. Acletoa tarazonae consistently formed a clade with Ahnfeltiopsis vermicularis and Chilean Gymnogongrus sp., and this clade was distinct from other genera in the Phyllophoraceae in the rbcL phylogeny. We also describe a new species of the Phyllophoraceae, Gymnogongrus caespitosus sp. nov., from northern Peru, characterized by a semirigid and flattened thallus, narrow branches, absence of hair cells, and cystocarps immersed in a single cavity. Ahnfeltiopsis concinna was not distinct from Ahnfeltiopsis durvillei, and consistently grouped in the genus Gymnogongrus sensu stricto in the rbcL phylogeny. A new combination of Gymnogongrus durvillei comb. nov. was made on the basis of A. durvillei, and A. concinna was merged with G. durvillei.

Neoharaldiophyllum, a new genus of Delesseriaceae (Rhodophyta) based on carposporophyte development and molecular data

AbstractThe new genus

Gracilaria corallicola and G. multipartita (Gracilariales, Rhodophyta), two related flattened European species

Two European species of Gracilaria possess flattened blades borne on cylindrical axes, namely, G. multipartita, known primarily from the Atlantic coast, and G. corallicola from the Mediterranean Sea. They are sister species that cluster with G. armata, G. bursa-pastoris and G. longa in rbcL analyses with strong bootstrap support. Blades of G. multipartita taper towards the tips, whereas those of G. corallicolla have broadly rounded tips. Spermatangia of G. corallicola are borne in shallow conceptacles (textorii-type) and data from the literature indicate that the same is true of G. multipartita. Cystocarp morphology is similar, with the gonimoblast filaments initially elongated, narrow and densely filled with cytoplasm, and with tubular nutritive cells issuing initially from lower gonimoblast cells and fusing with cells in the lowermost regions of the outer pericarp. Tetrasporangia are initiated terminally and displaced laterally with the production of side branches from the subterminal cell. The diagnostic characters of the Gracilariaceae are reviewed from a developmental perspective.

New record of Hypnea flexicaulis in New Zealand and description of Calliblepharis psammophilus sp. nov.

Abstract The genus Hypnea has been known in New Zealand for a long time but identification to species level has been difficult as only fragmentary and sterile material has been available for study and thus the genus has remained poorly known. Recently large amounts of Hypnea were collected in northern New Zealand enabling DNA sequencing and the presence of two species was confirmed: Hypnea flexicaulis which represents a new record for New Zealand, and Hypnea cornuta which was previously known from fragmentary material. Both of these species are regarded as introduced in other regions of the world. The new species described in this paper as Calliblepharis psammophilus was identified in the field as a species of Hypnea but morphological observations and molecular data confirmed it does not belong to this genus. It is characterized by caespitose thalli with irregularly branched terete axes and with tapering or curved tips, the axial cell enclosed by 5–7 pericentral cells, cortical cells packed tightly and not forming “rosettes” in surface view. The gonimoblast filaments originate from a fusion cell and develop outwardly in chains. This species is currently known from a single location in the North Island (south eastern coast), New Zealand.

Phylogeny, species diversity and biogeographic patterns of the genus Tricleocarpa (Galaxauraceae, Rhodophyta) from the Indo-Pacific region, including T. confertus sp. nov. from Taiwan

Among four different genera in Galaxauraceae, species diversity of the genus Tricleocarpa Huisman & Borowitzka is underestimated and requires further examination. In this study, we explored a molecular phylogeny of Tricleocarpa with an emphasis on Taiwan species and reassessed species diversity of the genus from the Indo-Pacific region based on analyses of rbcL and COI-5P sequences and morphological observations. The molecular analyses showed that species of Tricleocarpa examined are grouped into seven clades: six clades in the T. cylindrica group (the T. cylindrica complex, T. confertus, T. jejuensis, T. natalensis and two uncharacterized T. ‘cylindrica’ clades) and one clade as the T. fragilis group. Overall, at least 12 species in Tricleocarpa were detected from the Indo-Pacific region, including a new species, T. confertus S.-L. Liu & S.-M. Lin, from Taiwan. Among them, T. confertus can be separated from other species of Tricleocarpa by a thallus consisting of dichotomous or trichotomous, articulated and moniliform branches with smooth surfaces, constrictions at nodes and slightly anti-triangular in shape. The cystocarp morphology of T. confertus is similar to the T. cylindrica group by having paraphyses intermixing with gonimoblast filaments. Recognition of this new species from other species is also supported by the DNA-based, algorithmic species delimitation approaches. With the combination of molecular phylogeny and species diversity reassessment, our phylogeographic analysis supported a trend that species in the T. fragilis group are restricted in their distribution to subtropical and tropical areas whereas species in the T. cylindrica group have a wide distribution, ranging from temperate through to tropical areas.

A phylogenetic re-appraisal of the family Liagoraceae sensu lato (Nemaliales, Rhodophyta) based on sequence analyses of two plastid genes and postfertilization development.

The marine red algal family Liagoraceae sensu lato is shown to be polyphyletic based on analyses of a combined rbcL and psaA data set and the pattern of carposporophyte development. Fifteen of eighteen genera analyzed formed a monophyletic lineage that included the genus Liagora. Nemalion did not cluster with Liagoraceae sensu stricto, and Nemaliaceae is reinstated, characterized morphologically by the formation of the primary gonimolobes by longitudinal divisions of the gonimoblast initial. Yamadaella and Liagoropsis, previously placed in the Dermonemataceae, are shown to be independent lineages and are recognized as two new families Yamadaellaceae and Liagoropsidaceae. Yamadaellaceae is characterized by two gonimoblast initials cut off bilaterally from the fertilized carpogonium and diffusely spreading gonimoblast filaments. Liagoropsidaceae is characterized by at least three gonimoblast initials cut off by longitudinal septa from the fertilized carpogonium. In contrast, Liagoraceae sensu stricto is characterized by a single gonimoblast initial cut off transversely or diagonally from the fertilized carpogonium. Reproductive features, such as diffuse gonimoblasts and unfused carpogonial branches following postfertilization, appear to have evolved on more than one occasion in the Nemaliales and are therefore not taxonomically diagnostic at the family level, although they may be useful in recognizing genera.

Morphology and phylogenetic systematics of Ptilocladiopsis horrida and proposal of the Ptilocladiopsidaceae fam. nov. (Gigartinales, Rhodophyta)

:Detailed morphological and molecular analyses of Ptilocladiopsis horrida have resulted in the proposal of the Ptilocladiopsidaceae fam. nov. Molecular analyses placed the new family in the Gigartinales in a basal position relative to families that comprised the Dumontiaceae complex. Plants were erect, monopodial, and grew by transverse division of an apical cell. Each axial cell cut off four periaxial cells that progressively elongated and distally bore branched filaments. Inner cells of the branched filaments expanded progressively toward the outside to form a three-layered cortex bearing free filaments along the surface of the thallus. With the elongation of the periaxial cells, the basal cells of the branched filaments separated from the central axis to produce a hollow space around it. Spermatangial parent cells and carpogonial branches were produced from the innermost cells of the free filaments. Carpogonial branches were four-celled and strongly reflexed, with the trichogyne directed outwardly. The fertilized carpogonium fused with the third cell of the carpogonial branch and produced up to four connecting filaments, one of which could fuse with the supporting cell, which functioned as an auxiliary cell (procarpic condition); others elongated and fused with remote auxiliary cells (nonprocarpic condition). The auxiliary cell cut off a gonimoblast initial that differentiated into a primary gonimoblast cell bearing branched gonimoblast filaments, most of which matured into carposporangia. The primary gonimoblast cell fused with the auxiliary cell, which elongated to continue growth of the connecting filament. Mature gonimoblasts protruded from the thallus surface and were surrounded by a sparsely branched filamentous involucre. Tetrasporophytes have not been observed. Previous accounts failed to show the presence of connecting filaments, leading to the placement of Ptilocladiopsis in the procarpic order Ceramiales.

Crebradomus and Dissimularia, new genera in the family Chondrymeniaceae (Gigartinales, Rhodophyta) from the central, southern and western Pacific Ocean

:Two new genera of tropical-/subtropical-Pacific macroalgae are proposed. The monotypic Crebradomus gen. nov., based on C. gongylocarpus sp. nov., is restricted to Lord Howe Island in the southern Australasian-Pacific Ocean. Dissimularia gen. nov. consists of the type species, D. dactylocarpa sp. nov., from its Lord Howe Island type locality, as well as from the Hawaiian Islands, Guam and possibly Burma and the southern Great Barrier Reef, plus three geographically restricted, virtually cryptic species from small islands or atolls in Samoa and Micronesia. The long-problematical ‘Cryptonemia? umbraticola’ is shown on the basis of molecular studies of recent collections from its type locality, remote Palmyra Atoll, to represent a distinct species of Dissimularia, D. umbraticola comb. nov., with D. tauensis sp. nov. and D. withallii sp. nov. from Tau and Jarvis Islands, respectively, also belonging to this complex. Morphological features common to these taxa included turf-like, often imbricate thin blades of irregular contour, thalli that tended to occupy shaded habitats on coral reefs between 1.5- and 40-m depths, and blade sections that consisted of a shallow anticlinal cortex and a broad, lax to densely compact medulla of mostly periclinal filaments interspersed with varying numbers of anticlinally and obliquely traversing filaments. Only Crebredomus was found cystocarpic, the carposporophytes densely aggregated in verrucose marginal pods and consisting of a lengthy narrow fusion cell of irregular contours and a candelabra-shaped distal cluster of gonimoblast filaments bearing terminal chains of two or three carposporangia beneath a narrow ostiole. Male gametophytes and tetrasporophytes remain unknown in both genera. Molecular data indicated the generic distinctness of Crebradomus and Dissimularia, as well as the whole complex as members of the recently designated family Chondrymeniaceae of the order Gigartinales.

Tylotus laqueatus, a new species of Dicranemataceae (Gigartinales, Rhodophyta) from the Hawaiian Islands

SummaryA rarely collected shallow‐subtidal Hawaiian macroalga has been determined anatomically and molecularly to belong to an undescribed species of Tylotus J. Agardh, the most widely distributed genus of the small, mostly Australian‐endemic family Dicranemataceae. Thalli are repent and imbricate on calcareous boulders at the type locality on O‘ahu, and are anchored both basally and by haptera arising marginally and ventrally on the (sub‐)dichotomous, linear axes. Simple or forked terete haptera can be a means of perennation by the occasional direct issuing of adventitious blades. Fronds are multiaxial and consist of a broad pseudoparenchymatous medulla of thick‐walled cells surrounded on both sides by a two‐ or three‐layered small‐celled pigmented cortex in which numbers of ‘glandular’ hairs are embedded. Tetrasporangia are zonate, and gametophytes are monoecious. Carpogonial branches are three‐celled, directed to the thallus surface, and borne laterally on inner‐cortical supporting cells; cystocarps are prominently protuberant and scattered sparingly on dorsal frond surfaces, the carposporophytes directed outwardly beneath an ostiolate pericarp and connected to the parent gametophyte across a broad placental base in which the remnant auxiliary cell persists centrally. The inner surface of the pericarp is unusual in producing extensive patches or isolated islands of short gonimoblast filaments with terminal carposporangia as an apparent result of the implantation of gonimoblasts into the tissue of the lining. Anatomy indicates that the new species is more closely related to the East‐Asian Tylotus lichenoides Okamura than to the only other described member of the genus, the type species T. obtusatus (Sonder) J. Agardh from southern Australia. An rbcL phylogeny supports placement of sequences for Hawaiian specimens within the genus Tylotus but distinct from all previously recorded sequences of Tylotus. As is widely reported in other molecular‐phylogenetic analyses of the Gigartinales, we find that support for generic and familial relationships within the order is strong whereas that for between‐family relationships is low.

Molecular diversity of the calcified red algal genus Tricleocarpa (Galaxauraceae, Nemaliales) with the description of T. jejuensis and T. natalensis

Wiriyadamrikul J., Geraldino P.J.L., Huisman J.M., Lewmanomont K. and Boo S.M. 2013. Molecular diversity of the calcified red algal genus Tricleocarpa (Galaxauraceae, Nemaliales) with the description of T. jejuensis and T. natalensis. Phycologia 52: 338–551. DOI: 10.2216/13-155.1Tricleocarpa (Nemaliales) is a calcified, dichotomously branched red algal genus currently with two recognized species, T. cylindrica and T. fragilis, both widely distributed in warm temperate and tropical seas. We evaluated the relationships of Tricleocarpa using molecular markers, including 35 rbcL and 32 cox1 sequences, from specimens in the western Pacific, the Hawaiian Islands and South Africa. Our results demonstrated the presence of seven genetically distinct groups. The range of T. cylindrica was confirmed to include the West Indies, the Hawaiian Islands, and Asian waters, and specimens referable to T. fragilis were found in Asia. On the basis of our molecular analyses and detailed morphological examinations, we were able to discriminate two taxa that we here describe as new species: T. jejuensis sp. nov. and T. natalensis sp. nov. Tricleocarpa jejuensis, known from Korea, Japan, South Africa, and Taiwan, was distinguished by the presence of three to four cortical cell layers with elongated to compressed subsurface and innermost cells, monoecious sexuality, spherical cystocarps, and paraphyses intermixed with gonimoblast filaments. Tricleocarpa natalensis from Kwazulu-Natal, South Africa was characterized by three layers of elongate cortical cells, monoecious sexuality, hemispherical cystocarps, and paraphyses rarely intermixed with gonimoblast filaments. Our phylogenetic analyses indicated that three further clades were recognized at species level, but these were based on a few specimens and were not morphologically distinct; further sampling is needed in regions outside Asian waters before additional taxonomic revisions can be proposed.

Comparative morphology and systematics of Chondrymenia lobata from the Mediterranean Sea and a phylogeny of the Chondrymeniaceae fam. nov. (Rhodophyta) based on rbcL sequence analyses

The Chondrymeniaceae Rodríguez-Prieto, G. Sartoni, S.-M. Lin & Hommersand, fam. nov., is proposed for Chondrymenia lobata. Analyses of rbcL sequences place the new family in a large gigartinalean assemblage that comprises the Cystocloniaceae–Solieriaceae complex. Plants are decumbent and growth takes place by division of multiple apical cells at the margin of the blade. Thalli consist of an outer cortex of subspherical to elongate cortical cells arranged in anticlinal rows, a subcortex of cells cross-linked by lateral arms, and a large central medulla composed of primary medullary filaments intermixed with numerous rhizoidal filaments. Male stages are reported in monoecious individuals. Inactive carpogonial branches consist of a two-celled filament that is directed inwards from the supporting cell. Functional carpogonial branches are oriented outwardly, with the carpogonia and trichogynes pointed towards the thallus surface. After presumed fertilization, the carpogonium fuses with the hypogynous cell and transfers the zygote nucleus. The hypogynous cell, in turn, fuses with the supporting cell which contains many haploid nuclei. The resulting fusion cell functions as an auxiliary cell that cuts off a single gonimoblast initial, which produces the gonimoblast filaments. Gametophytic cells close to the auxiliary cell unite with it to form a placental fusion network of variable size and outline, and a placental fusion cell. Proximal gonimoblast cells fuse with the placental fusion cell, while the distal cells differentiate into branched chains of subspherical carposporangia. The superficial similarity of the outwardly developed osteolate cystocarp is responsible for Kylin's (1956) placement of Chondrymenia in his family Sarcodiaceae; however, the manner in which the placenta is formed is more like that seen in the Cystocloniaceae–Solieriaceae complex.

Molecular phylogeny and developmental studies of Apoglossum and Paraglossum (Delesseriaceae, Rhodophyta) with a description of Apoglosseae trib. nov.

Our morphological and molecular studies indicate that species from the southern hemisphere previously placed in Delesseria belong in Paraglossum and that Paraglossum and Apoglossum comprise a separate tribe, the Apoglosseae, S.-W. Lin, Fredericq & Hommersand, trib. nov., within the family Delesseriaceae. From a vegetative perspective the Apoglosseae is readily recognized because some or all fourth-order cell rows are formed on the inner sides of third-order cell rows. All fourth-order cell rows grow adaxially in Apoglossum, whereas both adaxial and abaxial cell rows are present in Paraglossum. Periaxial cells do not divide in Apoglossum, whereas they divide transversely in Paraglossum in the same way as in Delesseria. Major branches are formed mainly from the margins of midribs in the Apoglosseae. The procarp consists of a straight carpogonial branch and two sterile cells, with the second formed on the same side as the first. The carpogonium cuts off two connecting cells in tandem from its apical end, the terminal cell being nonfunctional and the subterminal cell typically fusing with the auxiliary cell. Gonimoblast filaments radiate in all directions from the gonimoblast initials and produce carposporangia terminally in branched chains, with pit connections between the inner gonimoblast cells broadening and enlarging. The auxiliary cell, supporting cell, and sterile cells unite into a fusion cell, which remains small in Apoglossum but incorporates the branched inner gonimoblast filaments and cells in the floor of the cystocarp in Paraglossum. Elongated inner cortical cells seen in mature cystocarps in the Delesserieae are absent in the Apoglosseae. Phylogenetic studies based on rbcL (RuBisCO large subunit gene) sequence analyses strongly support the recognition of the Apoglosseae within the subfamily Delesserioideae of the Delesseriaceae, in agreement with our previous observations based primarily on analyses of large subunit ribosomal DNA (LSU).

New features in the vegetative and reproductive morphology of Cystoclonium purpureum (Cystocloniaceae, Rhodophyta) from the North Atlantic Ocean

The seminal work of Kylin (1923, 1932, 1956) defined the family Cystocloniaceae (as the Rhodophyllidaceae) for genera having (1) a percurrent central-axial filament surrounded by a well-developed cortex; (2) procarps in which the auxiliary cell is one of the daughter cells borne immediately distal to the supporting cell of the carpogonial branch; (3) gonimoblast filaments that originate from a single initial directed either inwardly or laterally; and (4) zonately divided tetrasporangia. Most of the species currently placed in the Cystocloniaceae produce some kind of secondary gametophytic filaments in conjunction with gonimoblast development, although no such filaments have been reported in Cystoclonium purpureum or C. obtusangulum, the only two species currently recognized under Cystoclonium. Unlike the reports of previous studies, we observed an extensive system of short-celled secondary gametophytic filaments in C. purpureum that form regularly in association with gonimoblast initiation and continue their elaboration throughout gonimoblast and carposporangial development. Terminal cells of the secondary gametophytic filaments fuse with nearby fused and unfused gonimoblast cells throughout carposporophyte development. Secondary gametophytic filaments of one sort or another have been reported in nearly all other species placed in the Cystocloniaceae–Solieriaceae complex, often with linkage occurring between cells of the gonimoblast filaments and those of the secondary gametophytic filaments; however, the particular pattern of gametophyte–gonimoblast interaction described here in C. purpureum is, so far, unique among Rhodophyta.

Developmental morphology and systematics of Trematocarpus dichotomus (Sarcodiaceae, Rhodophyta) from Chile

Rodríguez-Prieto C. and Hommersand M.H. 2012. Developmental morphology and systematics of Trematocarpus dichotomus (Sarcodiaceae, Rhodophyta) from Chile. Phycologia 51: 586–595. DOI: 10.2216/11-122.1Trematocarpus dichotomus, the generitype of Trematocarpus Kützing, was restricted to the Pacific coast of South America from southern Peru to Chiloé in south-central Chile. Our investigation established that the vegetative thallus consists of an outer and inner cortex that encircles a medulla of uniformly separated, cylindrical to compressed filaments cross-linked by secondary pit connections. Spermatia were initially cleaved singly and released from the tip of an elongated spermatangium and later sequentially from a series of developing spermatia that matured basipetally within the spermatangium. Carpogonial branches were three-celled, initially directed outwardly but then curving sharply inwardly, the carpogonium producing an abruptly reflexed trichogyne. A single transverse division of the carpogonium after fertilization resulted in a proximal cell that fused with the first cell of the carpogonial branch, which became the generative auxiliary cell. The auxiliary cell cut off a single gonimoblast initial towards the thallus surface that branched beginning at the three-celled stage, with the cells in adjacent branches linking laterally by secondary pit connections. Surface cortical cells grew and branched to form a pericarp that split into inner and outer pericarp layers separated by a central cavity. Gonimoblast filaments were initially surrounded by inner pericarp from which they grew into the cavity and bore carposporangia terminally in branched chains. The gonimoblast filaments fused lengthwise progressively as they grew, and adjacent filaments linked laterally by secondary pit connections to form a fusion network referred to as the ‘gonimoblast reticulum’. Inner cells of the gonimoblast reticulum fused with cells of the inner pericarp, uniting the carposporophyte with the gametophyte through a basal placenta. Carposporangia may germinate in situ inside the cystocarp. Tetrasporangia were formed successively in nemathecia from elongated tetrasporangial initials on the concave sides of branches and were zonately divided. Several developmental stages documented here are newly reported for Trematocarpus and the family Sarcodiaceae.

Systematics of Liagora with diffuse gonimoblasts based on rbcL sequences and carposporophyte development, including the description of the new genera Neoizziella and Macrocarpus (Liagoraceae, Rhodophyta)

The genus Liagora is broadly defined and incorporates species with diverse carposporophyte developmental patterns, including species having compact gonimoblasts with discrete involucral filaments and species having diffuse gonimoblasts with intermingling involucral filaments and fused or unfused carpogonial branches. In order to clarify the phylogenetic significance of these patterns of cystocarp development, we inferred the species relationships of Liagora with diffuse gonimoblasts and related genera from the northwestern Pacific Ocean, based on rbcL sequence analysis. Molecular analyses demonstrated that Liagora is polyphyletic and the species currently recognized are clustered in three distinct clades. We revise the taxonomy by presenting new genera for two of these clades. The clade containing the generitype, L. viscida retains the name Liagora. The second clade, containing Liagora perennis, is described as Macrocarpus gen. nov. The third clade, for which we propose the new genus Neoizziella, contains Neoizziella asiatica sp. nov. and N. divaricata comb. nov. (basionym: Liagora divaricata C.K. Tseng). Neoizziella is characterized by morphologically similar, intermingling involucral and gonimoblast filaments, carpogonial branch cells that remain discrete, and small, undivided carposporangia. In contrast, Macrocarpus has larger, divided carposporangia, in addition to diffuse gonimoblasts with unfused carpogonial branches. The genera Akalaphycus and Stenopeltis, which also possess diffuse gonimoblasts, can be separated from these genera by a combination of cortical and carpogonial features.